Conventionally, there is known a linear conveyor configured to move a conveyor carriage (slider) along a rail on a base block, with use of a linear motor as a driving source (see e.g. JP 2011-98786A). In the linear conveyor, the conveyor path length may be extended depending on the purpose of use, or the conveyor carriage may be required to be dismounted, as necessary. In view of the above, it is often the case that a movable magnetic linear motor is employed as the linear motor. The movable magnetic linear motor has a linear motor stator constituted of electromagnets (field magnets) which are fixedly disposed on a base block in the form of an array, and a linear motor rotor constituted of a permanent magnet which is fixedly mounted on a conveyor carriage. The movable magnetic linear motor is configured to exert a force for impelling the conveyor carriage by controlling electric current supply to a coil constituting an electromagnet. The movable magnetic linear motor is provided with a linear scale constituted of a scale which is fixedly mounted on a conveyor carriage, and a number of sensors disposed on the base block side. It is possible to move the conveyor carriage to a specific position by controlling electric current supply to the electromagnet, based on a position of the conveyor carriage detected by the linear scale.
In the linear conveyor, the configuration (linear configuration or annular configuration) of a required conveyor path or a required conveyor path length may differ among the users. Further, the configuration of the conveyor path or the conveyor path length may be required to be changed afterwards. In order to meet with these demands in a simplified manner, there is proposed an idea of configuring a linear conveyor of unit members. Specifically, the following reasonable configuration is proposed. A unit member is constituted of the base block, a rail, electromagnets, and sensors of a linear scale. Then, a linear conveyor is configured by interconnecting a number of unit members to each other. A motor control device is disposed for each of the unit members. Then, electric current supply to the electromagnets in each of the unit members is individually controlled.
In the above configuration, the following matter should be taken into consideration. Each of the conveyor carriages has a movement error unique to each conveyor carriage due to a processing error or an assembling error. Accordingly, in order to position the conveyor carriages with high precision, it is necessary to know the unique movement errors in advance, and to correct the movement errors with respect to each of the conveyor carriages. In other words, in the case where a linear conveyor is constituted of a number of unit members, it is necessary to cause a motor control device of each of the unit members to store position correction data for use in correcting movement errors of the conveyor carriages, and to control electric current supply to the electromagnets, with use of the position correction data. Accordingly, in a linear conveyor including a large number of conveyor carriages, the operator is required to cause each of the motor control devices to store the position correction data for each of the conveyor carriages. This is cumbersome to the operator. Further, in the case where the configuration of a conveyor path or the conveyor path length is changed afterwards, or in the case where conveyor carriages are added afterwards, the operator is required to carefully manage whether position correction data is present in each of the motor control devices. If such a managing operation is not satisfactorily performed, it is difficult to secure positioning precision of conveyor carriages.